Apparatus for optical testing and sorting of objects, especially of food, which objects are serial conducted in free fall through a test zone, around which several light sources and reflex light receivers are arranged, light signals of which are transformed to electrical output signals which are compared in a controller with given lower and upper limits, thereby exeeding a control signal produced in a microprocessor, which controls a sorting shutter, which is arranged below the test zone.
This type of equipment is known from DE 36 14 400 C1, which shows optical test equipment intended for sorting objects, especially agrarian products like peas, beans, etc. All the objects are sorted out by a sorting shutter under the control of a fault signal. Inside the equipment the objects are illuminated by light sources distributed around the zone through which the objects fall. Light being reflected by the test objects is transmitted to light detectors. Signals from the light detectors are analyzed. The objects are illuminated by light bulbs which produce a total illumination of the objects, so that the light detectors register the object as a whole, including the background. As a result, the signals only give an overall result about the optical quality of the product, for example, the degree of ripeness. The damage spots, for example, a worm hole or a mold spot does not cause any indication within this equipment so that the operational usefulness of the device is limited. In addition, this equipment is only useful for the optical examination of dry objects because moist objects are shinny and the amount of light reflected from them depends on the angular relationship to the light detectors.
Another prior-art device is that of Key Technology Inc., USA, called Opti Sort (8/89). In this device the separated objects get scanned at high speed, from above by several electronic-cameras with opto-electrical line-transformers; which are called CCD-Arrays. Their signals get analyzed in relation to given boundary values. Due to the limited depth of focus of the camera-objective, this only allows, the exact registration of small objects with a fairly exact diameter or the same thickness, e.g. potatoe sticks. The camera equipment and the electronic analysis system demands great efforts and are very expensive.
The purpose of this invention is to reveal a relatively simple Optical Test-Equipment which safely analyses and sorts objects of extremely different sizes and different as well as surfaces with small shaped damages in different colours.